In general, a liquefied natural gas storage tank is used to store or transport cryogenic liquefied natural gas (LNG) of about −165° C. The liquefied natural gas storage tank is classified into a terrestrial storage tank (including a ground storage tank, a buried tank, and a semi-buried storage tank) which is installed on the ground or buried in the ground according to installation positions, and a mobile storage tank which is mounted on transportation means such as vehicles and ships.
Here, since the LNG storage tank stores LNG in a cryogenic state, there is a danger of explosion when the LNG storage tank is exposed to impact. For this reason, the structure of the LNG storage tank should satisfy conditions such as impact resistance and sealing performance. In order to satisfy such conditions, the LNG storage tank is configured to have a multi-layer wall structure. That is, the LNG storage tank includes a external tank (outer tank) in which a storage space is formed, an internal tank (inner tank) which directly contacts the LNG and seals the LNG, and a perlite interposed between the external tank and the internal tank to heat-insulate the LNG.
In particular, the ground storage tank included in the terrestrial storage tank is generally built as follows.
First, as a foundation construction for solidifying the ground, iron pipe wedges are hit on the ground, and concrete is poured on the ground so as to prevent earthquake or impact. After that, a construction is performed on a cylindrical side wall for determining the storage capacity of the ground storage tank on the basis of the foundation construction. Here, the construction of the side wall may be performed by injecting concrete into a mold and then removing the mold after the concrete (constituting an outer tank) is solidified. After that, the inner wall and bottom of the side wall are provided with a heat insulating panel, an internal tank is built inside the concrete outer tank, and a finishing process is then performed on the internal tank.
As described above, if the ground storage tank is constructed using the side wall, the concrete and the heat insulating panel cannot be built at the same time. Therefore, much time and manpower is required to build the concrete using the mold and then form the heat insulating panel on the concrete.